Nigel Farage has suggested the rising student star of Ukip's youth organisation denounced him as a racist and quit the party after being subject to "peer pressure" from other people at the London School of Economics.

On Tuesday Sanya-Jeet Thandi, a British-born Indian 20-year-old LSE student who had been a poster girl for the party, launched a savage attack Ukip for "exploiting the stupidity of ignorant anti-immigrant" voters.

Asked about her comments on Thursday, Farage told BBC Radio 4's World at One programme Thandi "may have been intimidated" into making them. Farage said Thandi had been promoting the party only a week ago. "I don't know quite why she changed her mind," he said.

“We haven't changed in seven days have we? Nothing had changed in seven days. Every comment, every image, every manifesto commitment in the European elections haven't changed. So she changed in seven days, we didn't. So it's surprising on that level.”

He added: "What's really more surprising is one 21 year-old who no longer held any position within the party at all - because since she had gone to the London School of Economics had been coming under a fair bit of peer pressure over being in Ukip - one 21 year-old leaves and it's a big story for the BBC."

Writing in The Guardian on Tuesday Thandi said: "This anti-immigrant campaign undermines Ukip's claim not to be a racist party. They are turning the election into a game of 'us' and 'them'. Well, I am with 'them'

"The direction in which the party is going is terrifying: Ukip has descended into a form of racist populism that I cannot bring myself to vote for. This week I decided to leave the party and I will abstain from voting in the upcoming European elections. I urge other Ukip supporters to do the same."

Thandi added: "Ukip is exploiting the stupidity of ignorant anti-immigrant voters for electoral gain. While the party deliberately attracts the racist vote, I refuse to be associated with them."